Jjp. Elich et Ja. Wieringa, TEMPERATURE EFFECTS INFLUENCING THE SPECTRAL AND TOTAL EMISSIVITY OF REFRACTORIES, Experimental thermal and fluid science, 10(3), 1995, pp. 318-326
The spectral reflectivity of some refractories has been measured. This
has been done to obtain specific (instead of general) data that will
be used in the modeling of radiative heat transfer in furnaces. The me
asurements were performed using an integrating sphere method. Because
of the lack of a diffuse reference sample for longer wavelengths, a pr
ocedure was developed for the use of a specular reference sample. Alth
ough the individual reflectivities follow the general trend, two chara
cteristics features can be reported. Refractory material that has not
been heated yet has a higher reflectivity than heated material in the
spectral range 2.5-4 mu m. This is attributed to water absorption. Ref
ractory material that came from the inner side of a combustion chamber
of a glass melting furnace showed different reflectivity behavior for
wavelengths smaller than about 5 mu m than that of material of the fu
rnace wall originating from a position about 20 cm away from the inner
side. The hemispherical emissivity as a function of temperature is lo
wered by the first effect and increased by the second. The magnitude o
f the effects can be up to 20%.